Chapter 24- The Digestive System Flashcards Preview

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Flashcards in Chapter 24- The Digestive System Deck (49):
1

What are the functions of the digestive system

Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion

2

Mesentaries

-Double sheets of serous membranes.

-Support portions of the digestive tract.

-Access route for vessels and nerves.

-Padding, protection, insulation, energy storage

3

Falciform ligament

Between the liver and body wall

4

Lesser omentum

- sickle shape (crescent)

- between the stomach and liver

5

Greater omentum

- from stomach to transverse colon

-fatty apron (“beer gut”)

6

Mesentery

- “proper”

- to small intestine

7

Mesenteries to the colon

Transverse Mesocolon

Sigmoid mesocolon

Mesocolon
-to remainder of large intestine

8

Retroperitoneal organs

-behind the peritoneal cavity

- duodenum (first part of small intestine)

-ascending/descending colon

-rectum

-kidneys

9

Mucosa

-inside, moistened by glandular secretions

-epithelium and lamina propria (loose CT)

-smooth muscle as muscularis mucosae

10

Submucosa

Dense irregular connective tissue

11

Muscularis externa

Smooth muscle-circular/longitudinal layers

12

Serosa

Serous membrane (wet, lubricated; surround organs)

13

Adventitia

Dense connective tissue

In oral cavity, pharynx, esophagus and rectum

14

Movement of digestive materials

-Rhythmic contractions

-Peristalsis

-Segmentation

15

Rhythmic contractions

Pacemaker cells

16

Peristalsis

Waves that move a bolus

17

Segmentation

(Squeeze food so it gets infiltrated by digestion fluids)

Churn and fragment a bolus

18

Enteric nervous system

- stretch receptors and chemoreceptors (detects chemicals in food)

-parasympathetic and local reflexes
-myenteric plexus (muscularis externa)
-submucosal plexus

19

Hormonal mechanisms

-Enteroendocrine cells

-Feedback through bloodstream

20

Local mechanisms

-Response to pH or chemical stimuli

-Prostaglandis, histamine (short range)
-signals broadcast to other cells

21

Functions of the oral (buccal) cavity

-analysis of material

-mechanical processing

-lubrication

-limited digestion

22

Functions of the tongue

-Assistance in chewing and swallowing

-Sensory analysis
-touch, temperature and taste

-Secretion of mucins and lingual lipase

23

Tongue movements

-Extrinsic and intrinsic muscles

-Innervated by hypoglossal nerve (CN 12)

24

Salivary glands

-parotid, sublingual (below tongue), submandibular (below jaw)

-saliva

25

Saliva

- electrolytes, buffers, mucins, antibodies, enzymes

-lubrication, moistening, dissolving

- salivary amylase (carbohydrate digestion)

26

Teeth (3 layers)

1) enamel- covering crown

2) dentin- forms basic structure

3) root- coated with cementum
-periodontal ligaments hold teeth in alveoli

27

Eruption of teeth

-20 primary teeth (aka: deciduous [milk] teeth)

-32 teeth of secondary dentition
-12 molars added

28

The Pharynx

-throat
-stratified squamous epithelium
-nasopharynx (behind nasal cavities)
-oropharynx (behind oral cavity)
-laryngopharynx (where vocal cords are)

29

The esophagus

-Nonkeratinized, stratified squamous epithelium
-Muscularis with skeletal muscle in upper third
-smooth muscle in lower third
-mixed in middle third(both skeletal and smooth)
-Lacks serosa
- anchored in the chest by adventitia
- Passes through the diaphragm (esophageal hiatus)

30

Functions of the stomach

-Bulk storage of undigested food
-Mechanical breakdown of food
-Disruption of chemical bonds in food
-acids and enzymes
-Production of intrinsic factor
- allows intestinal absorption of vitamin B12
-B12 required for erythropoiesis (red blood cells)

31

Anatomy of the stomach

-Cardia: superior, medial (close to heart)
-Fundus: above stomach-esophageal junction (base of fundamental)
-Body: between the fundus and curve of the J (major central portion)
-Pylorus: antrum and pyloric canal near duodenum(small intestine)
-Pyloric sphincter
-guards exit from stomach
-Rugae: ridges and folds in relaxed stomach
-Oblique muscle layer (extra)

32

Parietal cells

Intrinsic factor and HCl

33

Chief cells

Pepsinogen
-converted to a protease, pepsin, by acid

34

Pyloric Enteroendocrine Cells

- G cells which secrete gastrin
-stimulates stomach secretions

- D cells which secrete somatostain
- inhibits gastrin release

35

Digestion and absorption in the stomach

-Preliminary digestion of proteins(pepsin)

-Permits other digestion
-salivary amylase, lingual lipase
-slowly denature in acid

-Very little absorption of nutrients
-some drugs, however, are absorbed

36

Small intestine

-Extra secretions from pancreas,liver, gallbladder

-Simple columnar epithelium

-Ileocecal sphincter (valve)
-transition between small and large intestine

37

Histology of the small intestine

-Plicae: transverse folds

-Villi: fingerlike projections of the mucosa
- stick into lumen and increase SA tremendous

-Lacteals: terminal lymphatic in villus
- absorb dietary fats

38

Intestinal glands

Enteroendocrine, goblet and stem cells

39

Duodenum

- First 12 inches of small intestine

- Few plica (folds), villi

-Duodenal glands (Brunner’s)
-mucus to protect from acid
-buffers to neutralize acid in chyme
-urogastrone to inhibit gastric acid secretion
-helps inhibit activity in stomach

40

Jejunum

-Most absorption here

-Stores most nutrients

41

Ileum

-Peyer’s patches= lymphoid tissue
-protects from colon bacteria

42

Intestinal movements

Gastroenteric reflex (starts in stomach and affects intestines)
-initiated by stretch receptors in stomach
-stimulates intestinal motility

Gastroileal reflex (effect from stomach to ilium)
-small to large intestine
- triggers relaxation of ileocecal valve

Enterogastric reflex (sends signal to stomach to slow it down)
-slows gastric activity when duodenum already stretched by chime
- goes backward; negative feedback

43

The pancreas: endocrine and exocrine functions

Endocrine functions
-insulin and glucagon

Exocrine functions
- pancreatic juice secreted into small intestine
-carbohydrases, lipases, nucleases, proteases

44

Liver functions

-Metabolic regulation

-Hematological regulation
- blood reservoir
- makes plasma proteins
- phagocytosis of damaged blood cells (Kupffer cells)

-Bile production
-made in part from hemoglobin of old RBC
-colors feces

45

Liver histology

-Filters blood through sinusoids within lobules

1) Blood begins in the hepatic portal system
-drains all blood from intestines
-portal system= association between 2 capillary beds joined by veins

2) Hepatocytes treat the blood

3) Blood ends in the hepatic veins
- these join into the inferior vena cava

46

The gallbladder

-Stores bile
-bile emulsifies lipids in the small intestine
-lipid-bile salt complexes=micelles
-micelles diffuse into lacteals, then through the thoracic duct and at the left subclavian vein, released into the blood as chylomicrons

-Bile secreted from liver
-via right/left hepatic ducts
- join to make common hepatic duct

-Cystic duct carries bile to gallbladder for storage between meals

-Drains into small intestine through the common bile duct

47

Functions of the large intestine

Reabsorbs water
-compacts material into feces

Absorbs vitamins produced by bacteria
-vitamin K, B12, thiamine, riboflavin

Stores fecal matter prior to defecation

48

Histology of the large intestine

Absence of villi

Presence of goblet cells

Deep intestinal glands
-dominated by goblet cells (also called mucus cells)

49

The rectum

Stratified squamous epithelium

Internal and external anal sphincters
-Internal= involuntary smooth muscle
-External= voluntary skeletal muscle